1. Field of the Invention
The present invention relates to a digital image forming apparatus such as a digital copying machine wherein an image data can be stored in a memory.
2. Description of the Prior Art
There is known a digital copying machine which can store a digital image data of a document image obtained by an image reader and can produce a copy with use of the digital image data. In such a digital copying machine, because a digital image data of a document has been read and stored in a memory, when the same document is copied again, the read action is not need at the second copy and after.
However, a memory for storing digital image data has a limited memory capacity. Therefore, the timing of data clear is a problem when image data is stored fully in the memory.
In order to solve this problem, it is proposed to clear the image data stored in a memory after the copying action completes normally. Further, it is also proposed to clear the image data stored in a memory when a certain time passes after the completion of the copying action. However, in the two methods, when the same document is copied for example after the certain time passes, it is needed to read image data of the document again.
Further, it is also proposed to clear image data stored in a memory after a certain time passes from the time of data storage by using a clock provided in the copying machine. However, this approach needs a large capacity of memory to enhance the cost.